Method for managing radio link in multi-carrier environment, and device for same

ABSTRACT

A method for operating a terminal for radio link management includes: receiving from a first cell a connection reconfiguration message, for configuring carrier aggregation, including configuration information for a second cell; performing beam and radio link monitoring for the first and second cells; when a beam failure for the second cell is detected, performing at least one from among a procedure of reporting the beam failure to the first and second cells, a procedure of requesting the recovery of the beam failure from the first and second cells, and a beam recovery procedure for the second cell; receiving, from the first or second cell, a control message in response to the report of the beam failure, or in response to the beam recovery procedure; and, upon receiving the control message, determining whether the beam recovery procedure is successful.

TECHNICAL FIELD

The present invention relates to a method and an apparatus for radiolink management in a multi-carrier environment, and more particularly,to methods and apparatuses for mobility support and radio linkestablishment/management in a mobile communication system environmentsupporting carrier aggregation functionality, which uses a highfrequency band above a millimeter wave band.

BACKGROUND ART

In order to cope with the explosion of wireless data, a mobilecommunication system considers a 6 GHz to 90 GHz band as a transmissionfrequency for a wide system bandwidth. In such the high frequency band,it is assumed that a small base station is used due to deterioration ofreceived signal performance due to attenuation and reflection of radiowaves.

In order to deploy the mobile communication system based on small basestations each having a small service coverage, considering a millimeterfrequency band of 6 GHz to 90 GHz band, instead of implementing radioprotocol functions of the mobile communication system in each small basestation, considered is a method of configuring the mobile communicationsystem by utilizing a plurality of transmission and reception points(TRPs) through a functional split scheme, in which the base stationfunctions are divided into a plurality of remote radio transmission andreception blocks and one centralized baseband processing function block,or a carrier aggregation function.

In the mobile communication system employing such the functional splitor carrier aggregation function, mobility function support and radiolink establishment and management functions are required to guaranteeservice continuity in radio interfaces for a backhaul connecting a basestation and a core network, and a fronthaul connecting the remote radiotransmission and reception blocks (e.g., TRPs, Remote Radio Heads(RRHs), etc.) and the baseband processing block, as well as an accesslink between the base station and terminals.

DISCLOSURE Technical Problem

An objective of the present invention for solving the above-describedproblem is directed to providing a method for mobility support and radiolink management in a mobile communication system environment supportingcarrier aggregation, which uses a high frequency band above a millimeterwave band.

Another objective of the present invention for solving theabove-described problems is directed to providing an apparatus formobility support and radio link management in a mobile communicationsystem environment supporting carrier aggregation, which uses a highfrequency band above a millimeter wave band.

Technical Solution

An exemplary embodiment of the present invention for achieving theabove-described objective, as an operation method of a terminal forradio link management, may comprise receiving, from a first celloperating as a primary cell (PCell), a connection reconfigurationmessage for configuring a carrier aggregation function includingconfiguration information for a second cell operating as a secondarycell (SCell); performing beam and radio link monitoring operations forthe first cell and the second cell; in response to detecting a beamproblem or failure for the second cell, performing at least one of aprocedure of reporting the beam problem or failure for the second cellto the first cell and the second cell, a procedure of requestingrecovery of the beam problem or failure for the second cell to the firstcell and the second cell, and a beam recovery procedure with the secondcell; receiving a control message from the first cell or the second cellin response to the reporting of the beam problem or failure for thesecond cell or in response to the beam recovery procedure; anddetermining, according to reception of the control message, whether thebeam recovery procedure is successful.

The beam problem or failure may be reported to the first cell and thesecond cell together with identification information of a beam fromwhich the beam problem or failure is detected and information on a timeelapsed from a time point when the beam problem or failure is detected.

The beam problem or failure may be reported through transmission of acontrol field of a physical layer uplink control channel (PUCCH),transmission of a separate physical layer signal, or transmission of arandom access preamble, which uses an uplink active bandwidth part(BWP).

The control field of the PUCCH, the separate physical layer signal, orthe random access preamble may be configured for each of the first celland the second cell.

The beam problem or failure may be directly reported from the terminalto the first cell, or reported from the terminal to the first cellthrough the second cell or another secondary cell other than the secondcell.

The control message may be received through a control message of amedium access control (MAC) layer, a control message of a radio resourcecontrol (RRC) layer, a physical layer control channel, or a randomaccess response (RAR) message.

The control message may include at least one of information indicating achange to another beam, information indicating a newly activated beam,information configuring a new beam, and information indicating a changeof an active BWP.

The beam recovery procedure may be performed by transmitting a randomaccess preamble to the first cell or the second cell, or by transmittinga message for requesting a beam change to the first cell, anothersecondary cell capable of receiving uplink transmission other than thesecond cell, or the second cell that has successfully received therandom access preamble.

The random access preamble may be a non-contention-based random accesspreamble specified in the connection reconfiguration message.

When the random access preamble is a contention-based random accesspreamble, a contention-based random access preamble of the first cellmay be preferentially configured as the random access preamble, or whena random access resource is not configured in an uplink active BWP, acontention-based random access preamble of a cell configured as aninitial BWP may be preferentially configured as the random accesspreamble.

The random access preamble may be a non-contention-based random accesspreamble when a reception strength of a reference signal or asynchronization signal received through a beam in which the beam problemor failure is declared is greater than or equal to a reference value,and the random access preamble may be a contention-based random accesspreamble when the reception strength of the reference signal or thesynchronization signal received through the beam in which the beamproblem or failure is declared is less than a reference value.

The message for requesting the beam change may be reported throughtransmission of a control field of a PUCCH, transmission of a separatephysical layer signal, or transmission of a random access preamble,which uses an uplink active BWP.

Another exemplary embodiment of the present invention for achieving theabove-described objective, as an operation method of a terminal forradio link management, may comprise configuring a connection with afirst cell; determining whether feedback information or a physicaldownlink control channel (PDCCH) for uplink transmission to the firstcell is received from the first cell according to a preconfiguredcondition; in response to determining that the feedback information orthe PDCCH is not received according to the preconfigured condition,starting an uplink polling timer (UL_POLL_TIMER) and transmitting anuplink polling message to the first cell; in response to receiving anuplink polling response message or a downlink polling message for theuplink polling message from the first cell before the uplink pollingtimer expires, determining that a beam or radio link with the first cellis valid; and in response to not receiving the uplink polling responsemessage or the downlink polling message for the uplink polling messagefrom the first cell before the uplink polling timer expires, declaring afailure of the beam or radio link with the first cell.

The operation method may further comprise, when the failure of the beamor radio link with the first cell is declared, performing a beamrecovery procedure with the first cell or stopping uplink transmissionto the first cell for a preconfigured time.

The operation method may further comprise, when the failure of the beamor radio link with the first cell is declared, reporting the failure ofthe beam or radio link or requesting deactivation of the first cellthrough a second cell.

Yet another exemplary embodiment of the present invention for achievingthe above-described objective, as an operation method of a base stationoperating a primary cell (PCell) for radio link management, may comprisetransmitting, to a terminal, a connection reconfiguration message forconfiguring a carrier aggregation function including configurationinformation on a second cell operating as a secondary cell (SCell); inresponse to detecting a beam problem or failure for the second cell inthe terminal, performing a procedure of receiving a report of the beamproblem or failure for the second cell from the terminal and/or aprocedure of receiving a request of a beam recovery procedure for thesecond cell from the terminal; and transmitting a control message to theterminal in response to the report of the beam problem or failure forthe second cell or the beam recovery procedure. The beam problem orfailure may be reported from the terminal together with identificationinformation of a beam from which the beam problem or failure is detectedand information on a time elapsed from a time point when the beamproblem or failure is detected.

The beam problem or failure may be reported through transmission of acontrol field of a physical layer uplink control channel (PUCCH),transmission of a separate physical layer signal, or transmission of arandom access preamble, which uses an uplink active bandwidth part(BWP), and the control field of the PUCCH, the separate physical layersignal, or the random access preamble may be configured for each of thefirst cell and the second cell.

The beam problem or failure may be directly reported from the terminalto the first cell, or reported from the terminal to the first cellthrough the second cell or another secondary cell other than the secondcell.

The beam recovery procedure may be performed by receiving a randomaccess preamble from the terminal, performed by receiving a message forrequesting a beam change from the terminal, or performed by receiving amessage for requesting a beam change through another secondary cellcapable of receiving uplink transmission of the terminal other than thesecond cell or the second cell that has successfully received the randomaccess preamble.

Advantageous Effects

According to the exemplary embodiments of the present invention, in anXhaul network composed of wireless backhaul and fronthaul and an accesslink between the user terminals and the base station, efficient mobilitycontrols and signaling procedures for the wireless terminal or userterminal, which is mounted on a moving object such as an unmanned aerialvehicle, train, autonomous vehicle, and car using a navigation device,can be provided. Therefore, in the mobile communication system, mobilitysupport and radio link management functions for guaranteeing servicecontinuity can be provided.

DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual diagram illustrating a first exemplary embodimentof a wireless communication network.

FIG. 2 is a block diagram illustrating a first exemplary embodiment of acommunication node constituting a wireless communication network.

FIG. 3 is a conceptual diagram for explaining a structure of a mobilecommunication network to which exemplary embodiments of the presentinvention are applied.

FIG. 4 is a conceptual diagram for explaining in more detail a structureof a mobile communication network to which exemplary embodiments of thepresent invention are applied.

FIG. 5 is a conceptual diagram for explaining an example of configuringbandwidth parts in a 3GPP NR system to which exemplary embodiments ofthe present invention can be applied.

FIG. 6 is a conceptual diagram for explaining a mobility support methodaccording to an exemplary embodiment of the present invention.

FIG. 7 is a sequence chart for explaining a radio link management methodin a carrier aggregation environment according to an exemplaryembodiment of the present invention.

FIG. 8 is a sequence chart for explaining a radio link management methodin a carrier aggregation environment according to another exemplaryembodiment of the present invention.

MODES OF THE INVENTION

While the present invention is susceptible to various modifications andalternative forms, specific embodiments are shown by way of example inthe drawings and described in detail. It should be understood, however,that the description is not intended to limit the present invention tothe specific embodiments, but, on the contrary, the present invention isto cover all modifications, equivalents, and alternatives that fallwithin the spirit and scope of the present invention.

Although the terms “first,” “second,” etc. may be used herein inreference to various elements, such elements should not be construed aslimited by these terms. These terms are only used to distinguish oneelement from another. For example, a first element could be termed asecond element, and a second element could be termed a first element,without departing from the scope of the present invention. The term“and/or” includes any and all combinations of one or more of theassociated listed items.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directed coupled” to another element, there are nointervening elements.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of embodiments ofthe present invention. As used herein, the singular forms “a,” “an,” and“the” are intended to include the plural forms as well, unless thecontext clearly indicates otherwise. It will be further understood thatthe terms “comprises,” “comprising,” “includes,” and/or “including,”when used herein, specify the presence of stated features, integers,steps, operations, elements, parts, and/or combinations thereof, but donot preclude the presence or addition of one or more other features,integers, steps, operations, elements, parts, and/or combinationsthereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by thoseof ordinary skill in the art to which the present invention pertains. Itwill be further understood that terms defined in commonly useddictionaries should be interpreted as having a meaning that isconsistent with their meaning in the context of the related art and willnot be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

Hereinafter, exemplary embodiments of the present invention will bedescribed in greater detail with reference to the accompanying drawings.To facilitate overall understanding of the present invention, likenumbers refer to like elements throughout the description of thedrawings, and description of the same component will not be reiterated.

A wireless communication network to which exemplary embodimentsaccording to the present invention are applied will be described. Thewireless communication network to which exemplary embodiments accordingto the present invention are applied is not restricted to what will bedescribed below. That is, the exemplary embodiments according to thepresent invention may be applied to various wireless communicationnetworks. Here, the wireless communication network may be used with thesame meaning as a wireless communication system.

FIG. 1 is a conceptual diagram illustrating a first exemplary embodimentof a wireless communication network.

Referring to FIG. 1, a wireless communication network 100 may comprise aplurality of communication nodes 110-1, 110-2, 110-3, 120-1, 120-2,130-1, 130-2, 130-3, 130-4, 130-5, and 130-6. Each of the plurality ofcommunication nodes may support at least one communication protocol. Forexample, each of the plurality of communication nodes may support a codedivision multiple access (CDMA) based communication protocol, a widebandCDMA (WCDMA) based communication protocol, a time division multipleaccess (TDMA) based communication protocol, a frequency divisionmultiple access (FDMA) based communication protocol, an orthogonalfrequency division multiplexing (OFDM) based communication protocol, anorthogonal frequency division multiple access (OFDMA) basedcommunication protocol, a single carrier FDMA (SC-FDMA) basedcommunication protocol, a non-orthogonal multiple access (NOMA) basedcommunication protocol, a space division multiple access (SDMA) basedcommunication protocol, or the like. Each of the plurality ofcommunication nodes may have the following structure.

FIG. 2 is a block diagram illustrating a first exemplary embodiment of acommunication node constituting a wireless communication network.

Referring to FIG. 2, a communication node 200 may comprise at least oneprocessor 210, a memory 220, and a transceiver 230 connected to thenetwork for performing communications. Also, the communication node 200may further comprise an input interface device 240, an output interfacedevice 250, a storage device 260, and the like. Each component includedin the communication node 200 may communicate with each other asconnected through a bus 270.

The processor 210 may execute a program stored in at least one of thememory 220 and the storage device 260. The processor 210 may refer to acentral processing unit (CPU), a graphics processing unit (GPU), or adedicated processor on which methods in accordance with embodiments ofthe present disclosure are performed. Each of the memory 220 and thestorage device 260 may be constituted by at least one of a volatilestorage medium and a non-volatile storage medium. For example, thememory 220 may comprise at least one of read-only memory (ROM) andrandom access memory (RAM).

Referring again to FIG. 1, the wireless communication network 100 maycomprise a plurality of base stations 110-1, 110-2, 110-3, 120-1, and120-2, and a plurality of user equipments (UEs) 130-1, 130-2, 130-3,130-4, 130-5, and 130-6. Each of the first base station 110-1, thesecond base station 110-2, and the third base station 110-3 may form amacro cell, and each of the fourth base station 120-1 and the fifth basestation 120-2 may form a small cell. The fourth base station 120-1, thethird UE 130-3, and the fourth UE 130-4 may belong to cell coverage ofthe first base station 110-1. The second UE 130-2, the fourth UE 130-4,and the fifth UE 130-5 may belong to cell coverage of the second basestation 110-2. Also, the fifth base station 120-2, the fourth UE 130-4,the fifth UE 130-5, and the sixth UE 130-6 may belong to cell coverageof the third base station 110-3. The first UE 130-1 may belong to cellcoverage of the fourth base station 120-1. The sixth UE 130-6 may belongto cell coverage of the fifth base station 120-2.

Here, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1and 120-2 may refer to a node B (NodeB), an evolved NodeB (eNB), a basetransceiver station (BTS), a radio base station, a radio transceiver, anaccess point, an access node, or the like. Each of the plurality of UEs130-1, 130-2, 130-3, 130-4, 130-5 and 130-6 may refer to a terminal, anaccess terminal, a mobile terminal, a station, a subscriber station, amobile station, a portable subscriber station, a node, a device, or thelike.

Each of the plurality of communication nodes 110-1, 110-2, 110-3, 120-1,120-2, 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 may support acellular communication (e.g., long term evolution (LTE), LTE-A(advanced), etc. defined in the 3rd generation partnership project(3GPP) standard), or wireless protocol specifications of mmWave (e.g., 6GHz to 80 GHz band) based wireless access technology. Each of theplurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 mayoperate in the same frequency band or in different frequency bands. Theplurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may beconnected to each other via an ideal backhaul or a non-ideal backhaul,and exchange information with each other via the ideal or non-idealbackhaul. Also, each of the plurality of base stations 110-1, 110-2,110-3, 120-1, and 120-2 may be connected to the core network (not shown)through the ideal or non-ideal backhaul. Each of the plurality of basestations 110-1, 110-2, 110-3, 120-1, and 120-2 may transmit a signalreceived from the core network to the corresponding UE 130-1, 130-2,130-3, 130-4, 130-5, or 130-6, and transmit a signal received from thecorresponding UE 130-1, 130-2, 130-3, 130-4, 130-5, or 130-6 to the corenetwork.

FIG. 3 is a conceptual diagram for explaining a structure of a mobilecommunication network to which exemplary embodiments of the presentinvention are applied, and FIG. 4 is a conceptual diagram for explainingin more detail a structure of a mobile communication network to whichexemplary embodiments of the present invention are applied.

Referring to FIG. 3, an exemplary embodiment of a method of connecting abase station and a core network in a mobile communication network usingfronthaul and backhaul is shown. In a cellular communication network, abase station 310 (or macro base station) or a small base station 330 maybe connected to a termination node 340 of the core network by a wiredbackhaul 380.

Here, the termination node 340 of the core network may be a ServingGateway (SGW), a User Plane Function (UPF), a Mobility Management Entity(MME), an Access and Mobility Function (AMF), or the like.

In addition, when base station functions are configured as split into abaseband processing function block 360 (e.g., a baseband unit (BBU) or acloud platform) and a remote radio transmission and reception node 320(e.g., a remote radio head (RRH) or a transmission & reception point(TRP)), the baseband processing function block 360 and the remote radiotransmission and reception node 320 may be connected through a wiredfronthaul 370.

The baseband processing function block 360 may be located at the basestation 310 that supports a plurality of remote radio transmission andreception nodes 320 or may be configured as a logical function betweenthe base station 310 and the termination node 340 of the core network tosupport multiple base stations. In this case, functions of the basebandprocessing function block 360 may be physically configured independentlyof the base station 310 and the termination node 340 of the corenetwork, or may be installed and operated at the base station 310 (orthe termination node 340 of the core network).

Each of the remote radio transmission and reception nodes 320, 420-1,and 402-2 of FIGS. 3 and 4, and each of the base stations 110-1, 110-2,110-3, 120-1, 120-2, 310, 330, 431-3, and 431-4 of FIGS. 1, 3, and 4 maysupport OFDM, OFDMA, SC-FDMA, or NOMA based downlink transmission anduplink transmission with terminals.

In addition, when the remote radio transmission and reception nodes ofFIGS. 3 and 4 and the plurality of base stations of FIGS. 1, 3, and 4support a beamforming function using an antenna array in a transmissioncarrier of a mmWave band, services may be provided without interferencebetween beams within the base station through the respectively formedbeams, and services for a plurality of terminals (or user equipments(UEs)) may be provided within one beam.

In addition, each of the plurality of base stations 110-1, 110-2, 110-3,120-1, 120-2, 310, 330, 471, and 472 may support a multi-inputmulti-output (MIMO) transmission (e.g., a single-user MIMO (SU-MIMO), amulti-user MIMO (MU-MIMO), a massive MIMO, or the like), a coordinatedmultipoint (CoMP) transmission, a carrier aggregation (CA) transmission,a transmission in unlicensed band, a device-to-device (D2D)communication (or, proximity services (ProSe)), or the like. Here, eachof the plurality of UEs 130-1, 130-2, 130-3, 130-4, 130-5, 130-6, 410-1,410-2, 410-3, and 410-4 may perform operations corresponding to theoperations of the plurality of base stations 110-1, 110-2, 110-3, 120-1,and 120-2, and operations supported by the plurality of base stations110-1, 110-2, 110-3, 120-1, 120-2, 310, 330, 431-3, and 431-4. Forexample, the second base station 110-2 may transmit a signal to thefourth UE 130-4 in the SU-MIMO manner, and the fourth UE 130-4 mayreceive the signal from the second base station 110-2 in the SU-MIMOmanner. Alternatively, the second base station 110-2 may transmit asignal to the fourth UE 130-4 and fifth UE 130-5 in the MU-MIMO manner,and each of the fourth UE 130-4 and fifth UE 130-5 may receive thesignal from the second base station 110-2 in the MU-MIMO manner. Each ofthe first base station 110-1, the second base station 110-2, and thethird base station 110-3 may transmit a signal to the fourth UE 130-4 inthe CoMP transmission manner, and the fourth UE 130-4 may receive thesignal from the first base station 110-1, the second base station 110-2,and the third base station 110-3 in the CoMP manner. Each of theplurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 mayexchange signals with the corresponding UEs 130-1, 130-2, 130-3, 130-4,130-5, or 130-6 which belongs to its cell coverage in the CA manner.Each of the base stations 110-1, 110-2, and 110-3 may coordinate D2Dcommunications between the fourth UE 130-4 and the fifth UE 130-5, andthus the fourth UE 130-4 and the fifth UE 130-5 may perform the D2Dcommunications under coordination of each of the second base station110-2 and the third base station 110-3.

Then, operation methods of communication nodes in a mobile communicationnetwork will be described. Even when a method (e.g., transmission orreception of a signal) to be performed in a first communication nodeamong communication nodes is described, a corresponding secondcommunication node may perform a method (e.g., reception or transmissionof the signal) corresponding to the method performed in the firstcommunication node. That is, when an operation of a terminal isdescribed, a corresponding base station may perform an operationcorresponding to the operation of the terminal. Conversely, when anoperation of the base station is described, the corresponding terminalmay perform an operation corresponding to the operation of the basestation.

In the following description, the SGW is a termination node of a corenetwork for exchanging data packets with a base station providingservices to a user terminal using a radio access protocol. Also, the MMEis an entity in charge of a control function in a radio access section(or interface) for user terminals in a wireless communication network.Thus, in the following description, the present invention is not limitedto the specific terms ‘SGW’ or ‘MME’. That is, the above-described termsmay be replaced with other terms indicating a function that supports aradio access protocol according to a radio access technology (RAT) or anentity that performs the corresponding function according to aconfiguration of the core network.

Referring to FIG. 4, an exemplary embodiment of a configuration of aradio link between nodes to which functional split is applied is shown.When the functional split is applied, a node of a radio access networkmay be classified into a central unit (CU) and a distributed unit (DU).

The CU 432-1 or 432-2 (e.g., gNB-CU in the 3GPP-based NR systems) is alogical node that controls operations of one or more DUs and performsradio resource control (RRC), service data adaptation protocol (SDAP),or packet data convergence protocol (PDCP) functions according to an RRCprotocol and a PDCP protocol.

The DU 431-1, 431-2, 431-3, 431-4, 431-5, or 431-6 (e.g., gNB-DU in theNR system) may be a logical node that performs functions of a radio linkcontrol (RLC) layer, a medium access control (MAC) layer, and a PHYlayer, or partial functions of the PHY layer. One DU may support one ormore cells, and one cell may support only one DU. The operation of theDU may be partially controlled by the CU, and the DU may be connected tothe CU through an F1 interfaces 450-1, 450-2, or 450-3.

In addition, a DU (e.g., 431-2 or 431-6) for relaying may be present ina connection section between the DUs 431-1 and 431-4 and the CUs 432-1and 432-2 according to configuration, roles, or properties of the nodesfor the functional split. In this case, the interfaces between the DUs431-1 and 431-4 and the DUs 431-2 and 431-6 may be connected throughrelay links 451-1 and 451-2. In addition, the DU 431 may be connectedwith the TRPs (or RRHs) 420-1 and 420-2 in a wired or wireless manner,or may be configured as integrated in the base stations 431-3 and 431-4.

Meanwhile, in the 3GPP NR system using the millimeter frequency band, abandwidth part (BWP) concept is applied to secure flexibility of channelbandwidth operation for packet transmission. The base station mayconfigure up to four BWPs having different bandwidths to the terminal.The BWPs may be configured independently for downlink and uplink. EachBWP may have not only a different bandwidth but also a differentsubcarrier spacing (SCS).

FIG. 5 is a conceptual diagram illustrating an example of configuringbandwidth parts in a 3GPP NR system to which exemplary embodiments ofthe present invention can be applied.

As shown in FIG. 5, a BWP is a bandwidth configured for transmission andreception of the terminal. The BWPs (i.e., BWP1, BWP2, BWP3, and BWP4 ofFIG. 5) may be configured not to be larger than a system bandwidth 601supported by the base station.

For example, BWP1 is configured with 10 MHz bandwidth having 15 kHz SCS,BWP2 is configured with 40 MHz bandwidth having 15 kHz SCS, BWP3 isconfigured with 10 MHz bandwidth having 30 kHz SCS, and BWP4 isconfigured with 20 MHz bandwidth having 60 kHz SCS.

The BWP may be classified into an initial BWP, an active BWP, or anoptional default BWP. The terminal may perform an initial accessprocedure with the base station using the initial BWP. One or more BWPsmay be configured through an RRC connection configuration message, andone of them may be configured as the active BWP. The terminal and thebase station may transmit or receive data packets using the active BWPamong the configured BWPs, and the terminal may perform a controlchannel monitoring operation for packet transmission and reception withrespect to the active BWP.

In addition, the terminal may switch from the initial BWP to the activeBWP or the default BWP, or may switch from the active BWP to the initialBWP or the default BWP. Such the BWP switching may be performed based onan indication of the base station or a timer. The indication of the basestation for switching the BWP may be transmitted to the terminal usingRRC signaling or a DCI of a physical downlink control channel, and theterminal may switch to the BWP indicated by the received RRC signalingor DCI. For example, in the NR system, when an RA resource is notconfigured in the active UL BWP, the terminal may switch from the activeUL BWP to the initial UL BWP in order to perform a random accessprocedure.

Mobility Support Method

FIG. 6 is a conceptual diagram illustrating a mobility support methodaccording to an exemplary embodiment of the present invention.

Referring to FIG. 6, a case in which a beamforming function is appliedbetween the base station and the terminal is shown. In the followingdescription, it is assumed that a signal transmitted by the base stationis used to provide an inter-base station mobility function or to selectan optimal beam within the base station. However, a signal transmittedby the terminal may be used for the purpose.

In FIG. 6, the terminal 502-1 or 502-2 may be in a state of establishinga connection with the base station 501-1, 501-2, or 501-3 and receivingservices from the base station, in a state of establishing a connectionwith the base station 501-1, 501-2, or 501-3, or in a state of existingwithin a service coverage of the corresponding base station withoutestablishing a connection therewith.

In a mobile communication system using a base station to whichbeamforming techniques are applied in a high frequency band, a functionof changing a beam configured between the base station and the terminal502-1 in the base station 501-1, and a mobility support and radioresource management function of changing beams configured between theterminal 502-2 and the base stations 501-2 and 501-3 may be considered.

For example, when a beam #3 of the base station 501-1 and a beam #2 ofthe terminal 502-1 are configured (or, beam paired), and services areprovided by the base station 501-1, according to a change of radiochannel quality, the beam used between the base station 501-1 and theterminal 502-1 may be changed from the beam #3 of the base station toanother beam (e.g., beam #2 or beam #4) of the base station.Alternatively, the beam used between the base station 501-1 and theterminal 502-1 may be changed from the beam #2 of the terminal toanother beam (e.g., beam #3, beam #1, or beam #4) of the terminal.

Meanwhile, the terminal 502-2, which has configured a beam with the basestation 501-2, may perform a mobility support and radio resourcemanagement function based on a handover procedure, which changes thebeam currently in use to a beam of the adjacent base station 501-3according to a change in radio channel quality.

In order to perform the mobility support and radio resource managementfunction, the base station may transmit a synchronization signal or areference signal for the terminal to search or monitor. In case of abase station using a frame format supporting a plurality of symbollengths to support multi-numerology, monitoring by the terminal may beperformed for a synchronization signal or a reference signal configuredwith an initial numerology, default numerology, or default symbollength.

Here, the initial numerology or the default numerology may be aconfiguration of a frame format applied to radio resources in which aUE-common search space is configured, a frame format applied to radioresources in which a control resource set (CORESET) ZERO (or, CORESET#0) of physical downlink control channels of the 3GPP new radio accesstechnology (New RAT, NR) system is configured, or a frame format appliedto radio resources through which a synchronization symbol burst foridentifying a cell in the 3GPP NR system is transmitted.

Here, the frame format may refer to information on configurationparameters (e.g., values of the configuration parameters, offset, index,identifier, range, periodicity, or interval (or, duration), etc.) suchas a subcarrier spacing (SCS) configuring a radio frame (or subframe), acontrol channel configuration (e.g., configuration of CORESET), a symbol(or slot) configuration, a reference signal configuration, or the like.The information on the frame format may be transferred to the terminalusing system information or a dedicated control message.

In addition, the terminal, which has configured a connection with thebase station, may perform a beam management operation by monitoring aconfigured beam or an activated beam through transmission of an uplinkdedicated reference signal configured by the base station or receptionof a downlink dedicated reference signal configured by the base station.

For example, the base station 501-1 may transmit a synchronizationsignal (SS) and/or a downlink reference signal so that terminals in itsservice coverage can search for itself to perform downlinksynchronization maintenance, beam configuration, or radio linkmonitoring operations. Also, the terminal 502-1, which has configured aconnection with the serving base station 501-1, may receive physicallayer radio resource configuration information for connectionconfiguration and radio resource management from the serving basestation.

Here, the physical layer radio resource configuration information maymean configuration parameters in RRC control messages of the LTE or NRsystem such as PhysicalConfigDedicated, PhysicalCellGroupConfig,PDCCH-Config, PDCCH-PDCCH-ConfigSIB1, ConfigCommon, PUCCH-Config,RACH-ConfigCommon, RACH-ConfigDedicated, RadioResourceConfigCommon,RadioResourceConfigDedicated, ServingCellConfig,ServingCellConfigCommon, or the like, and may include the followinginformation. The configuration information may include parameter valuessuch as a configuration (or allocation) periodicity of a correspondingsignal (or radio resource) based on a frame format of a base station (ortransmission frequency), position information of a radio resource fortransmission in a time domain/frequency domain, a transmission (orallocation) time, or the like. Here, the frame format of the basestation (or transmission frequency) may mean a frame format having aplurality of symbol lengths according to a plurality of SCS within oneradio frame to support multi-numerology. That is, the number of symbolsconstituting mini-slots, slots, and subframes that exist within oneradio frame (e.g., a frame of 10 ms) may be configured differently.

(1) Configuration information of transmission frequency and frame formatof base station

-   -   Transmission frequency information: information on all        transmission carriers (i.e., cell-specific transmission        frequency) in the base station, information on BWPs in the base        station, information on a transmission time reference or time        difference between transmission frequencies in the base station        (e.g., transmission periodicity or offset parameter indicating        the transmission reference time (or time difference) of the        synchronization signal), etc.    -   Frame format information: configuration parameters of a        mini-slot, slot, subframe that supports a plurality of symbol        lengths according to SCS.

(2) Configuration information of downlink reference signal (e.g.,channel state information-reference signal (CSI-RS), common referencesignal (Common-RS), etc.)

-   -   Configuration parameters such as a transmission periodicity, a        transmission position, a code sequence, or a masking (or        scrambling) sequence for a reference signal commonly applied in        the coverage of the base station (or beam).

(3) Configuration information of uplink control signal

-   -   Configuration parameters such as a sounding reference signal        (SRS), uplink beam sweeping (or beam monitoring) reference        signal (RS), uplink grant-free radio resources, or uplink radio        resources (or RA preamble) for random access, etc.

(4) Configuration information of physical downlink control channel(PDCCH)

-   -   Configuration parameters such as a reference signal for PDCCH        demodulation, a beam common reference signal (e.g., a reference        signal that can be received by all terminals in a beam        coverage), a beam sweeping (or beam monitoring) reference        signal, a reference signal for channel estimation, etc.

(5) Configuration information of physical uplink control channel (PUCCH)

-   -   Scheduling request signal configuration information    -   Configuration information for a feedback (ACK or NACK)        transmission resource for supporting HARQ functions, etc.    -   Number of antenna ports, antenna array information, beam        configuration or beam index mapping information for application        of beamforming techniques    -   Configuration information of downlink and/or uplink signals (or        uplink access channel resource) for beam sweeping (or beam        monitoring)    -   Configuration information of parameters for beam configuration,        beam recovery, beam reconfiguration, or radio link        re-establishment operation, a beam change operation within the        same base station, a reception signal of a beam triggering        handover execution to another base station, timers controlling        the above-described operations, etc.

In case of a radio frame format that supports a plurality of symbollengths for supporting multi-numerology, the configuration (orallocation) periodicity of the parameter constituting theabove-described information, the time-domain and frequency-domainposition information of the radio resource, or the transmission (orallocation) time may be information configured for each correspondingsymbol length (or subcarrier spacing).

In the following description, ‘Resource-Config information’ may refer toa control message for radio resource configuration including at leastone parameter among the above-described physical layer radio resourceconfiguration information. In the following description, a property orsetting value (or range) of an information element (or parameter)transmitted by the corresponding control message may have a meaning,rather than the name of ‘Resource-Config information’. Thus, theinformation element (or parameter) conveyed by the Resource-Configcontrol message may be radio resource configuration information which iscommonly applied to the entire base station (or beam) coverage ordedicatedly allocated to a specific terminal (or terminal group). Theconfiguration information of the above-described Resource-Configinformation may be configured as one control message or may beconfigured as different control messages according to the property ofthe configuration information. In addition, the beam index may berepresented without distinction between transmission beam indexes andreception beam indexes by using an index (or identifier) of a referencesignal mapped or associated with the corresponding beam, or an index (oridentifier) of a transmission configuration indicator (TCI) state forbeam management.

Therefore, the terminal 502-1 in the connected state may be providedwith services through a beam configured with the base station 501-1. Forexample, when the beam #3 of the base station 501-1 and the beam #2 ofthe terminal 502-1 are configured (or beam paired) for the terminal toreceive services, the terminal 502-1 may search or monitor a downlinkradio channel by using a downlink synchronization signal (e.g., asynchronization signal block (SSB) of the 3GPP NR system) and a downlinkreference signal (e.g., CSI-RS of the NR system) of the beam #3 of thebase station. Here, that the beams are configured (or beam paired) andservices are provided may mean that packets are transmitted or receivedthrough an activated beam among one or more configured beams. In the3GPP NR system, activation of a beam may mean that a configured TCIstate is activated.

Through such the radio link monitoring (RLM) operation, the terminal502-1 may detect a radio link problem. Here, the detection of a radiolink problem means that there is an error in configuring or maintainingphysical layer synchronization for the corresponding radio link. Thatis, this means that it is detected that the physical layersynchronization of the terminal has not been maintained for a certaintime. When a radio link problem is detected, a radio link recoveryoperation may be performed. If the radio link problem is not recovered,a radio link failure (RLF) may be declared, and a radio linkre-establishment procedure may be performed.

A physical layer (Layer 1 or physical layer), Layer 2 functions such asMedium Access Control (MAC), Radio Link Control (RLC), Packet DataConvergence Protocol (PDCP), etc., or Layer 3 functions such as RadioResource Control (RRC) of the radio protocol constituting the radio linkmay participate in the procedures such as the detection of a physicallayer problem in a radio link, the radio link recovery, the radio linkfailure detection (or declaration), and the radio link re-establishmentaccording to the radio link monitoring operation.

The physical layer of the terminal may receive a downlinksynchronization signal and/or a reference signal (RS) to monitor theradio link. In this case, the reference signal may be a base stationcommon reference signal (Common RS) or a beam common reference signal,or a dedicated reference signal allocated to the terminal (or terminalgroup). Here, the common reference signal refers to a reference signalthat can be received by all terminals within the coverage (or servicearea) of the corresponding base station or beam to estimate a channel.In addition, the dedicated reference signal refers to a reference signalthat can be received and used for channel estimation only by a specificterminal or terminal group within the coverage of the base station orthe beam.

Therefore, when the base station or the configured beam is changed, thededicated reference signal for managing the changed beam may be changed.This means that a procedure for selecting another beam from among thebeams configured through the configuration parameters between the basestation and the terminal or changing the configured beam is required. Inthe 3GPP-based NR system, changing the beam means that an index ofanother TCI state is selected among the indexes (or identifiers) of theconfigured TCI states or a new TCI state is configured and changed to anactive state. Configuration information on the common reference signalmay be obtained by the terminal through system information.Alternatively, in case of a handover in which the base station ischanged or in case of connection reconfiguration, the base station maytransmit the configuration information on the common reference signal tothe terminal through a dedicated control message.

In order to provide service continuity between the base station and theterminal, a method in which the terminal provides services by allocatinga plurality of beams to one terminal may be considered. For example, inFIG. 6, the base station 501-1, 501-2, or 501-3 may allocate a pluralityof beams to the terminal 502-1 or 502-2. That is, the base station 501-1may allocate the beam #2, the beam #3, and the beam #4 to the terminal502-1. Alternatively, the base station 501-2 may allocate the beam #3and the beam #4 to the terminal 502-2.

In this case, the plurality of beams may be allocated in considerationof moving speed, moving direction, location information, radio channelquality, or beam interference of the corresponding terminal. Forexample, when the moving speed of the terminal 502-1 is slow, the basestation 501-1 may allocate the beams #2 and #3 adjacent to each other tothe terminal 502-1. However, when the moving speed of the terminal 502-1is fast, the base station 501-1 may allocate the beams #2 and #4 to theterminal 502-1, which are not adjacent to each other and are separatedfrom each other.

When the terminal 502-2 moves to the base station 501-3 while receivingservices by being allocated the beams #3 and #4 from the base station501-2, if the base station 501-2 and the base station 501-3 are basestations belonging to different cells (or sectors), the terminal 502-2may perform a handover procedure. During the handover, the terminal502-2 may receive information on the configuration of the beams #1 and#2 of the base station 501-3 from the base station 501-2 through ahandover control message. Meanwhile, the information on the beams #1 and#2 may be obtained by the base station 501-2 through a procedure inwhich the terminal 502-2 reports measurement results for thetarget/neighbor base station 501-3 to the base station 501-2.

In this case, the information on configuration of the beams may includeat least one of index information of a transmission or reception beamconfigured according to a beam monitoring or beam measurement result,configuration information (e.g., transmission power, beamwidth,vertical/horizontal angle, etc.) of the corresponding beam, transmissionor reception timing information (e.g., index, offset value, or the likeof subframe, slot, mini-slot, symbol, etc.) of the corresponding beam,configuration information of a reference signal of the correspondingbeam, and sequence information or index information of a referencesignal of the corresponding beam.

In order to allocate a plurality of beams as described above, theplurality of beams allocated between the base stations 501-2 and 501-3and the terminal 502-2, and the moving state (moving speed, movingdirection, location information, etc.) of the terminal, the beammonitoring and measurement results, etc. may be reported or transferredas included in a signaling control message for performing the handover.

In addition, when the terminal 502-2 moves to the base station 501-3while receiving services by being allocated the beams #3 and #4 from thebase station 501-2, if the base station 501-2 and the base station 501-3are base stations belonging to the same cell (or sector), an intra-celltransmission node change procedure may be performed. Here, the basestation 501-2 and the base station 501-3 may be nodes (e.g., RRH, TRP,node to which a radio protocol functional split is applied, etc.) inwhich the radio protocols such as physical layer, MAC layer, RLC layer,PDCP layer, adaptation layer, or RRC layer, which constitute a radioaccess network, are partially configured. In this case, the adaptationlayer (e.g., service data adaptation protocol (SDAP) layer of the NRsystem) is a layer higher than the PDCP, and performs functions such asmapping between a QoS flow and a data radio bearer (DRB) or marking of aQoS flow identifier for downlink (or uplink) packets.

As such, in the base stations belonging to the same cell, when the radioprotocol layers for the radio access network are partially configuredexcluding the RRC layer, a base station change procedure from the basestation 501-2 to the base station 501-3 for the terminal 502-2 may beperformed through the exchange of control messages of the MAC layer(e.g., MAC control element (CE) or control PDU) without exchangingcontrol messages of the RRC layer.

That is, which layer of the radio protocol layers is responsible forgenerating and transmitting/receiving the control messages for the basestation change may be determined according to up to which of the radioprotocol layers for the radio access network the corresponding basestation (e.g., 501-2 or 501-3 of FIG. 6) is configured to include.

For example, if the base station 501-2 and the base station 501-3 areconfigured to include the MAC layer (or RLC layer), the control messagesfor the base station change may be generated at a higher layer than theMAC layer (or RLC layer), and transmitted or received between theterminal and the base station, and the MAC function (or, MAC functionand RLC function) of the terminal and the base station should be newlyconfigured after being reset.

However, when the base station 501-2 and the base station 501-3 areconfigured to include only a part of the MAC layer or are configuredonly with physical layer functions, the control messages for the basestation change may be generated in the MAC layer, and transmitted orreceived between the terminal and the base station, and the base stationchange may be performed without resetting the MAC function of theterminal and the base station.

When the change of the base station (or transmission node) describedabove occurs, information for identifying the corresponding transmittingbase station may be transferred to the terminal by using a controlmessage of the RRC layer or the MAC layer, or a physical layer controlchannel according to configuration conditions of the radio protocollayers of the base station (e.g., 501-2, 501-3). In this case, theinformation for identifying the transmitting base station (ortransmission node) may include an identifier of the base station (ortransmission node), reference signal information, information on aconfigured beam (or configured TCI state), information on a sequence (orscrambling) identifier for the base station (or transmission node), orthe like.

The reference signal information may be a radio resource of a referencesignal allocated for each transmitting base station, sequenceinformation or index information of the reference signal, or sequenceinformation or index information of a dedicated reference signalallocated to the terminal. Here, the radio resource of the referencesignal may mean parameters indicating a symbol position on a time axisat which the reference signal is transmitted and a relative or absolutesubcarrier position on a frequency axis within a radio resource regionsuch as a frame, subframe, or slot. Such the parameter may berepresented by a number or the like sequentially assigned to index,symbol, or subcarrier, which represents a corresponding radio resourceelement or radio resource set. Hereinafter, the reference signalinformation may refer to the above-described transmission periodicity,the code sequence or masking (or scrambling) of the reference signal,the radio resource of the reference signal, index information, or thelike. The reference signal identifier may refer to a parameter (e.g.,resource ID, resource set ID) that can distinguish the correspondingreference signal information uniquely among one or more reference signalinformation.

The information on the configured beam may be an index (or identifier)of the configured beam (or configured TCI state), configurationinformation of the corresponding beam (e.g., transmission power,beamwidth, vertical/horizontal angle, etc.), transmission or receptiontiming information (e.g., an index or an offset value of subframe, slot,mini-slot, symbol, etc.) of the corresponding beam, or reference signalinformation or reference signal identifier information corresponding tothe corresponding beam.

Accordingly, the terminal may identify a target base station (ortransmission node) to perform a beam monitoring operation, a radioaccess operation, or a transmission/reception operation of a control (ordata) packet by using identification information of the transmittingbase station (or transmission node), which the base station transmitsusing the control message of the RRC layer or the MAC layer, or thephysical layer control channel.

In the case where a plurality of beams are configured, the base stationand the terminal may transmit and receive packet information with allthe configured beams, and the number of downlink beams may be the sameas or different from the number of uplink beams. For example, aplurality of downlink beams from the base station to the terminal may beconfigured, and one uplink beam from the terminal to the base stationmay be configured.

Alternatively, when a plurality of beams are configured, the basestation and the terminal may not transmit and receive packet informationwith all the configured beams, and some of the configured plurality ofbeams may be configured as reserved (or candidate) beam(s) not fortransmitting and receiving packet information. For example, theconfigured plurality of beams may be configured in form of primary beam,secondary beam, or reserved (or candidate) beam(s). In the NR system,such the configuration of the plurality of beams may mean that theconfigured TCI state identifiers (IDs) are configured in form ofprimary, secondary, or reserved.

For example, the primary beam (e.g., primary TCI state ID) may mean abeam capable of transmitting and receiving data and control signaling,and the secondary beam (e.g., secondary TCI state ID or deactivated TCIstate ID) may mean a beam capable of transmitting and receiving onlydata packets excluding control signaling. Here, the exclusion of thecontrol signaling may be performed by a method of restricting thecontrol signaling of physical layer, layer 2 (e.g., layer 2 such as MAC,RLC, PDCP, etc.), or layer 3 (e.g., layer 3 such as RRC, etc.) accordingto each layer, a method of partially restricting them according tofunctions within the layer, or a method of restricting them according tothe type of the control message. However, the type of control messagemay mean a type of control message generated or transmitted/receivedaccording to operational functions of the radio protocol such asdiscontinuous transmission/reception (DRX/DTX) operations,retransmission operations, connection configuration and managementoperations, measurement/reporting operations, operations of a pagingprocedure, operations of an access procedure, etc.

In addition, the reserved (or candidate) beam (e.g., reserved TCI sateID or deactivated TCI state ID) may be limited in transmission andreception of data or signaling packets. Also, the reserved (orcandidate) beam may be configured as a beam on which the base station orthe terminal performs only beam monitoring operations for beam matching(or configuration) or performs only measurement and reportingoperations. Accordingly, measurement results for the reserved (orcandidate) beam may be reported using the primary beam or the secondarybeam. The measurement or reporting on the reserved (or candidate) beammay be performed in accordance with a related configuration parameter orperiodically or aperiodically in accordance with a determination orevent condition of the terminal. In particular, the report of theresults of measurement or beam monitoring on the reserved (or candidate)beam may be transmitted using a physical layer control channel, such asa physical uplink control channel (PUCCH) of the LTE (or NR) system, ora control message of the MAC layer (e.g., a form such as MAC controlPDU). Here, the result of the beam monitoring may refer to measurementresults of one or more beams (or beam groups) as results of the beammonitoring (or beam sweeping) operation on the formed beam of the basestation, which is performed by the terminal.

Based on the report of results of beam measurement or beam monitoring,the base station may change the property (e.g., primary beam, secondarybeam, reserved (or candidate) beam, active beam, or deactivated beam) ofthe beam (or property of the TCI state). Here, when the TCI state ischanged, the property of the TCI state may be changed to a primary TCIstate, a secondary TCI state, a reserved (or candidate) TCI state, aconfigured TCI state, an active TCI state, a deactivated TCI state, orthe like.

As described above with respect to the property of the TCI state, astate in which a data packet or control signaling can be transmitted orreceived even in a limited manner, such as the primary TCI state or thesecondary TCI state, may be assumed as the active TCI state or a servingTCI state. Also, a state in which it is a target of measurement ormanagement, but data packets or control signaling cannot be transmittedor received, such as the reserved (or candidate) TCI state, may beassumed as the deactivated TCI state or configured TCI state.

The change of the property of the beam (or TCI state) may be controlledat the RRC layer or the MAC layer. When changing the property of a beam(or TCI state) at the MAC layer, the MAC layer may notify the higherlayer of the beam property change. In addition, the change of beamproperty may be transferred to the terminal using a control message ofthe MAC layer or a physical layer control channel (e.g., a physicaldownlink control channel (PDCCH) of the LTE (or NR) system). Here, whenthe physical layer control channel is used, the control information maybe configured in form of downlink control information (DCI), uplinkcontrol information (UCI), or a separate indicator (or fieldinformation) of the LTE (or NR) system.

The terminal may request to change the TCI state property based on thebeam measurement or monitoring results. The control information orfeedback information for requesting the change of the TCI state propertymay be transmitted using a physical layer control channel, a MAC layercontrol message, or an RRC control message. The control message,signaling information, or feedback information for changing the TCIstate property may be configured using at least one or more parametersfrom the above-described information on configured beam.

The property change of the beam (or TCI state) described above may meana change from the active beam to the deactivated beam or reserved (orcandidate) beam, or a change from the primary beam to the secondary beamor reserved (or candidate) beam, or vice versa. That is, it means thatthe property of the beam is changed between the beam propertiesdescribed above, and the change of beam property may be performed in theRRC layer or the MAC layer. If necessary, the beam property change maybe performed through partial cooperation between the RRC layer and theMAC layer.

In addition, when a plurality of beams are allocated, a beam fortransmitting a physical layer control channel may be configured andoperated. That is, a physical layer control channel may be transmittedusing all the multiple beams (e.g., the primary beam or the secondarybeam) or a physical layer control channel may be transmitted using onlythe primary beam.

Here, the physical layer control channel is a channel such as PDCCH orPUCCH of the LTE (or NR) system, and may transmit scheduling informationincluding radio resource element (RE) allocation and modulation andcoding scheme (MCS) information, channel quality indication (CQI),precoding matrix indicator (PMI), feedback information such as HARQACK/NACK, resource request information such as scheduling request (SR),beam monitoring result (or TCI state ID) for supporting beamformingfunction, measurement information on active or inactive beams, or thelike.

In case that the physical layer control channel is transmitted usingonly a downlink primary beam transmitted from the base station to theterminal, the feedback information may be received through the physicallayer control channel of the primary beam or data transmitted throughthe secondary beam may be demodulated and decoded using controlinformation obtained through the physical layer control channel of theprimary beam.

Alternatively, in case that the physical layer control channel istransmitted using only an uplink primary beam transmitted from theterminal to the base station, scheduling request information or feedbackcontrol information may be transmitted through the physical layercontrol channel of the primary beam.

In the case of the multiple beam allocation (or TCI state configuration)described above, parameters indicating allocated (or, configured) beamindexes for the multiple beams (or TCI states), spacing between theallocated beams, or whether or not contiguous beams are allocated may betransferred through signaling between the base station and the terminal.Signaling for such the beam allocation may be configured differentlyaccording to a report from the terminal such as moving speed, movingdirection, or location information of the terminal, or moving state,moving speed, moving direction, and location information of theterminal, or the quality of radio channel, which the base station canrecognize or obtain by other means. Here, the quality of radio channelmay refer to a signal quality of a radio channel represented by achannel state indicator (CSI), a Received Signal Strength Indicator(RSSI), a Reference Signal Received Power (RSRP), a Reference SignalReceived Quality (RSRQ), or the like.

In the above description, the radio resource may be configured byfrequency-axis parameters such as center frequency, system bandwidth,subcarriers, or the like and time-axis parameters according to a unit oftransmission (or reception) time (or, periodicity, interval, window)such as radio frame, subframe, transmission time interval (TTI), slot,mini-slot, symbol, or the like. Additionally, the radio resource mayrefer to a resource occupied for transmission in the radio section byapplying a hopping pattern of the radio resource, a beam formingtechnique using multiple antennas (e.g., beam configuration information,beam index), or a code sequence (or bit sequence or signal sequence). Incase of such the radio resource, the name of the physical layer channel(or transport channel) may vary according to the type (or property) ofdata or control message to be transmitted, uplink, downlink, sidelink(or side channel), or the like.

Such the reference signal for beam (or TCI state) or radio linkmanagement may include a synchronization signal such as asynchronization signal (SS) or a synchronization signal block (SSB), achannel state information reference signal (CSI-RS), a phase tracking(PT-RS), a sounding reference signal (SRS), a demodulation referencesignal (DM-RS), or the like. A reference parameter for reception qualityof the reference signal for beam (or TCI state) or radio link managementmay be configured as a parameter such as a measurement unit time, ameasurement interval, a reference value indicating a degree of improvedchange, a reference value indicating a degree of deteriorated change, orthe like. The measurement unit time or measurement interval may beconfigured as an absolute time reference (e.g., ms, sec, etc.),transmission timing interval (TTI), a radio channel configuration suchas symbol, slot, (sub)frame, scheduling periodicity, etc., an operationperiodicity of the base station or terminal, or the like. Also, thereference value representing the degree of change in reception qualitymay be configured as an absolute value (dBm) or a relative value (dB).Also, the reception quality of the reference signal for beam (or TCIstate) or radio link management may be represented by Reference SignalReceived Power (RSRP), Reference Signal Received Quality (RSRQ),Received Signal Strength Indicator (RSSI), Signal-to-Noise Ratio (SNR),Signal-to-Interference Ratio (SIR), or the like.

Beam Management Procedure

The measurement or monitoring operation for beam (or TCI state) or radiolink management described above may be performed by the base station orthe terminal. The base station or the terminal may perform themeasurement or monitoring operation according to the parametersconfigured for the measurement operation or monitoring, and the terminalmay report measurement results according to configuration parameters forthe measurement reporting.

According to the measurement result, when the reception quality of thereference signal satisfies a predetermined reference value and/or apreconfigured timer condition, the base station may determine (or,trigger) deactivation (or activation) or the like of the beam accordingto the beam (or radio link) management, beam switching, or beam blockagesituation, and transmit a control message indicating a related operationto the terminal.

In addition, when the reception quality of the reference signalaccording to the measurement result satisfies the configured referencevalue and/or preconfigured timer condition, the terminal may report themeasurement result or may transmit a control message triggering (orrequesting) deactivation (or activation) of the beam according to thebeam (or radio link) management operation, beam switching (or TCI stateID change or property change), or the beam blockage situation to thebase station.

The basic operation procedure for the beam (or TCI state) managementthrough radio link monitoring may include a beam failure detection(BFD), a beam recovery (BR), or a beam failure recovery (BFR) requestprocedure, or the like for the radio link. The function for determiningthe beam failure detection or beam recovery operation and triggering therelated procedures, control signaling, or the like may be performed bythe physical layer, the MAC layer, the RRC layer, or the like incooperation, or the related function may be performed by them aspartially divided.

The physical layer of the terminal may estimate whether the physicallayer is kept synchronized (or, quality of a physical layer controlchannel) through monitoring of the radio link (or physical layerchannel) and transmit the result to a higher layer. The estimationresult may be transmitted to the higher layer in form of an in-syncindication (hereinafter referred to as ‘IS Ind’) or an out-of-syncindication (hereinafter referred to as ‘OoS Ind’) in the correspondingmonitoring interval.

The higher layer of the terminal receiving the IS Ind or OoS Ind fromthe physical layer may determine whether or not the radio link ismaintained by counting the number of corresponding indicationscontinuously received or based on a timer. In case of the timer-basedoperation, if the IS Ind is not received again until a preconfiguredtimer expires after receiving the OoS Ind, the beam failure detection(BFD) may be determined (or declared) for the corresponding radio link.

Such the detection (or declaration) may be performed at the MAC layer.For example, the MAC layer of the terminal may determine that a physicallayer problem occurs if the OoS Ind is continuously received by apreconfigured value ‘N’ or if the IS Ind is not received from thephysical layer until a preconfigured timer (e.g., timer for Beam FailureDetection (TBFD)) expires after receiving the OoS Ind. Here, N is apositive integer, and the timer TBFD starts when the OoS Ind is receivedafter receiving the IS Ind, and is reset when the IS Ind is received.

Alternatively, if the uplink transmission to the base station does notsucceed until a predetermined condition is satisfied, the terminal maydetermine (or declare) the beam failure detection. For example, in caseof transmitting through an uplink grant-free resource or transmitting anuplink resource request (SR), if feedback information or a responsemessage confirming successful reception of the correspondingtransmission is not received from the base station even after thetransmission is performed (or attempted) by a preconfigured number oftimes, the terminal may determine (or declare) the beam failuredetection. Also, the terminal may determine (or declare) the beamfailure detection even when a control message instructing to adjust atransmission timer of the uplink physical channel is not received fromthe base station before a preconfigured timer expires.

In case of the beam failure detection (BFD) of the radio link, theterminal may perform a beam recovery operation. For beam recovery, theterminal may transmit a physical layer control channel or referencesignal pre-allocated for beam recovery or perform a random accessprocedure. Also, such the uplink transmission for beam recovery may beconfigured to be repeatedly transmitted until an associated timerexpires, and the related configuration information may be transmitted inadvance to the terminal using system information or a separate controlmessage. Here, when performing the beam recovery through a random accessprocedure, beam recovery completion or failure may be determined basedon a successful completion condition of the random access operation or arelated timer. Also, when performing the beam recovery through thetransmission of the physical layer control channel or the referencesignal that is pre-allocated for beam recovery, whether the beamrecovery succeeds or fails may be determined based on a condition ortimer (e.g., timer for beam recovery (TBR)) for determining success orfailure of the beam recovery. The parameter or timer TBR for configuringthe reference condition for determining the beam recovery success orfailure may be configured as a cell-specific parameter or a UE-specificparameter, and may be notified to the terminal using system informationor a dedicated control message.

For example, when a random access procedure is performed fornotification of the beam failure detection or the beam recovery failureor for the beam recovery, a random access resource may be allocated tothe corresponding terminal so as to perform a non-contention-basedrandom access. Here, the random access resource may be a configurationparameter for transmitting a physical random access channel (PRACH), andmay include a random access preamble (i.e., PRACH) index, a PRACHmasking parameter, a preamble format for transmitting the PRACH, a timeresource for transmitting the PRACH, a frequency resource fortransmitting the PRACH, radio resource allocation information fortransmitting a random access response message, a window value or relatedtimer information for receiving the random access response message, orthe like.

If the terminal does not receive the corresponding random accessresponse until a preconfigured timer expires, the terminal mayadditionally perform a contention-based random access procedure fornotification of the beam failure detection or beam recovery failure orfor the beam recovery operation.

Alternatively, when performing the beam recovery operation bytransmitting the physical layer control channel or reference signalallocated in advance, the terminal may perform the beam recoveryoperation by transmitting the corresponding control information orreference signal according to a preconfigured parameter (e.g., a timeror the number of transmissions).

When a result of performing the beam recovery operation does not satisfya beam recovery success condition, the MAC layer of the terminal mayreport a final beam recovery failure to the RRC layer. The RRC layer,which has received control information notifying the beam recoveryfailure from the MAC layer, may determine a radio link failure (RLF) dueto the beam recovery failure and perform a radio link re-establishmentprocedure. In this case, the terminal may transmit a radio linkre-establishment request message by setting a cause of the RLF to thebeam recovery failure or beam failure.

Radio Link Management Method in Carrier Aggregation Environment Acarrier aggregation (CA) function refers to a function in which oneterminal configures connections with a plurality of cells. Through thesupport of the CA function, the terminal may transmit or receivesignaling packets, traffic data packets, DCI, UCI, feedback information,or the like through a physical layer data channel (e.g., physicaldownlink shared channel (PDSCH), physical uplink shared channel (PUSCH))or a physical layer control channel (e.g., PDCCH, PUCCH) with aplurality of cells connected to the terminal.

When the terminal receives services from a plurality of cells using suchthe CA function, a primary cell (PCell) and at least one secondary cell(SCell) may be configured for the terminal.

FIG. 7 is a sequence chart for explaining a radio link management methodin a carrier aggregation environment according to an exemplaryembodiment of the present invention.

Referring to FIG. 7, the base station 702 (i.e., primary cell) maydetermine support of the CA function for the terminal 701 (S705). Thebase station 702 may operate as a primary cell and exchange signalingmessages for connection reconfiguration for configuring the CA function,which include configuration information on a secondary cell 703 or 704,with the terminal 701 (S706). In the step S706, the primary cell 702 maytransmit, to the terminal 701, a connection reconfiguration message(i.e., RRC connection reconfiguration message) including controlparameters for supporting the CA function. In the step S706, theabove-described non-contention-based random access preamble for the beamfailure or beam problem detection report or for the beam recovery may beconfigured for one or more BWPs or active BWPs configured in theterminal in units of a cell supporting the CA function.

The terminal 701 receiving the connection reconfiguration messageincluding the CA configuration parameters for the secondary cell 703 or704 from the primary cell may transmit a connection reconfigurationcomplete message (e.g., RRC connection reconfiguration complete message)notifying the successful reception of the corresponding control messageto the primary cell 702. Meanwhile, when the secondary cells areconfigured on an SCell group basis, the secondary cell 704 may mean anSCell (i.e., PUCCH SCell) capable of transmitting PUCCHs among theSCells constituting the SCell group. That the SCells are configured on agroup basis may mean that the same parameters may be applied to theSCells belonging to the corresponding SCell group.

After completing the configuration of the CA function through thesignaling procedure of the step S706, the terminal may perform beam andradio link monitoring operations for the PCell 702 and the SCells 703and 704 (S707). In this case, the beam failure detection and beamrecovery operation methods described above may be applied to a basicbeam management operation in each cell. That is, the beam managementoperation of the terminal may be independently performed with respect tothe PCell or SCell according to the method described above.

In addition to the independent beam management operation, cellssupporting the CA function may be controlled to perform an additionaloperation for the beam management operation of the SCell. For example,when a beam problem or failure of the SCell is detected according to thebeam management operation, the terminal 701 may report the beam failureor beam problem for the SCell, or may request a beam recovery procedure,or may report that the beam recovery procedure has been performed orcompleted to the PCell or PUCCH SCell before performing the beam failuredeclaration or the beam recovery operation or independently ofperforming the operation (S708). In this case, information on a timeelapsed from when the beam failure detection is recognized orinformation on a time elapsed from the beam problem/failure detection tothe beam recovery completion may be transmitted together withinformation for identifying the corresponding beam of the SCell byapplying the above-described configuration parameters. Here, theinformation for beam identification may be a TCI state ID or a referencesignal (e.g., SSB, CSI-RS, etc.) identifier for beam monitoring.

The reporting of the beam problem or failure detection, the beamrecovery request reporting, or the beam recovery completion reporting inthe step S708 may be independently performed by the terminal 701 to eachof the cells 702, 703, or 704 supporting the CA function. Also, theSCell 703 or 704 that receives a control message informing the beamproblem or failure detection report, the beam recovery request report,or the beam recovery completion report from the terminal 701 maytransfer the relevant information to the PCell 702 (S708-1). The controlmessage of the step 708-1 may be transferred using a base stationinternal control message, a control message between base stations, or acontrol message between functional nodes (e.g., DU or CU of FIG. 4)constituting a base station (or cell).

The cell 702, 703, or 704 that receives the control message informingthe beam problem or failure detection report, the beam recovery requestreport, or the beam recovery completion report from the terminal 701 maytransmit a response message for the message of the step S708 to theterminal 701 (S709). The control message of the step S709 may refer to acontrol message including beam reconfiguration information or indicatingbeam reconfiguration. Such the control message may be transmitted usinga MAC layer control message, an RRC layer control message, or a physicallayer control channel. Here, the message including the beamreconfiguration information or indicating the beam reconfiguration maybe composed of one or more of information indicating a change to anotherbeam, information indicating a newly activated beam, information forconfiguring a new beam, or information indicating a change of an activeBWP.

On the other hand, after performing the step S708 or without performingthe step S708, the terminal 701 may transmit a control message for beamrecovery (e.g., random access preamble or message requesting beamchange) to perform a beam recovery procedure for the cell in which thebeam failure or beam problem is detected (S710).

That is, the terminal 701 may report the beam problem or beam failuredetection, request the beam recovery procedure, or perform the beamrecovery procedure by performing only one of the steps S708 and S710described above.

In the step S710, the RA preamble transmitted by the terminal for beamrecovery may be transmitted to the cell (SCell) in which the beamfailure or beam problem has been detected or transmitted to the PCell(or a cell in which the RA preamble resource is configured). Inaddition, the ‘control message for requesting beam change’ using thecontrol message of the MAC layer, the control message of the RRC layer,or the physical layer control channel described above may be transmittedto the cell in which a beam failure or beam problem is not detected anduplink transmission is possible (e.g., PCell or PUCCH SCell) or theSCell in which the aforementioned random access is successful.

The SCell 703 or 704 receiving the control message for beam recovery(e.g., random access preamble or message for requesting beam change)from the terminal 701 may transfer relevant information to the PCell 702(S710-1). The control message of the step S710-1 may be delivered usinga base station internal control message, a control message between basestations, or a control message between functional nodes constituting abase station (or cell).

The cell 702, 703, or 704 that receives the control message for beamrecovery from the terminal 701 may transmit a response message for themessage of the step S710 to the terminal 701 (S711). The cell performingthe step S711 may be different according to the following cases.

-   -   Case1: When the PCell 702 or the PUCCH SCell 704 performs the        step S711        -   Case where the terminal performs the step S708 and/or S709            with the PCell (or PUCCH SCell), and the PCell (or PUCCH            SCell) transmits a response message    -   Case2: When the SCell 703 performs the step S711        -   Case where the terminal performs the step S708 and/or S709            with the SCell        -   Case where the terminal performs the step S708 and/or S709            with the PCell (or PUCCH SCell), and the PCell (or PUCCH            SCell) transfers the corresponding information to the SCell

The control message of the step S711 may refer to a control messageincluding beam reconfiguration information or indicating beamreconfiguration. The control message of the step S711 may be transmittedusing a control message of the MAC layer, a control message of the RRClayer, or a physical layer control channel including the beamreconfiguration information, or using a random access response message.Here, the message including the beam reconfiguration information orindicating the beam reconfiguration may be composed of one or more ofinformation indicating a change to another beam, information indicatinga newly activated beam, information for configuring a new beam, orinformation indicating a change of an active BWP.

In performing the steps S708 to S711, the terminal 701 may perform onlyone step into which the step S708 and the step S710 are integrated toreport the detection of the beam problem or beam failure, to request thebeam recovery, or to perform the beam recovery procedure. In this case,the base station 702, 703, or 704 may transmit a control message forbeam recovery or reconfiguration to the terminal 701 by performing onlyone step into which the step S709 and the step S711 are integrated. Thecontrol message for beam recovery or reconfiguration transmitted by thebase station to the terminal may be transmitted using a MAC layercontrol message, an RRC layer control message, or a physical layercontrol channel as described in the step S709 or S711, and thecorresponding control message may be information indicating a TCI stateID, a CSI-RS index, or an SSB index, or information (or indicator)indicating activation for the corresponding beam.

In case that the PCell 702 transmits such the control message, thecontrol message may include information on an identifier(s) of SCelland/or BWP which is a beam recovery or beam reconfiguration target.

The terminal 701, which has performed the reporting of the beam failureor the beam recovery operation through the step S708 and/or the stepS710, may determine whether the recovery has failed (or succeeded)according to a result of the control message reception operation of thestep S709 and/or the step S711 from the cell 702, 703, or 704 (S712).Upon detecting or determining the beam recovery failure or the radiolink failure in the step S712, the terminal 701 may transmit a controlmessage for connection re-establishment to the cell 702, 703, or 704(S713).

When the terminal performs a non-contention-based RA procedure toperform the step S708 or S710, the terminal may notify the beam failuredetection or the beam recovery failure, or perform the beam recoveryoperation through a non-contention-based RA resource configured in thestep S706 for the corresponding cell.

When the terminal performs a contention-based random access procedure toperform the step S708 or step S710, the terminal may give priority to acontention-based RA resource of the PCell. Alternatively, when the RAresource is not configured in the uplink active BWP, the terminal mayperform the RA procedure by giving priority to a contention-based RAresource of the cell configured as the initial BWP.

In the CA function supporting environment, the terminal 701 and the basestations 702, 703, or 704 may not necessarily perform all the stepsdescribed in FIG. 7 for the beam management and beam recovery. Inparticular, each step from S708 to S713 may be selectively performed.For example, depending on the configuration of the system or the basestation, the capability of the terminal, or the service situation, eachstep of the steps S708 to S713 may be selectively performed to performoperations and signaling procedures for the beam management and the beamrecovery.

In addition to the method or procedure using FIG. 7, after detecting thebeam failure for the SCell, the terminal may start a timer (e.g., theabove-described beam recovery timer (T_(BR)) or an additional timer(e.g., timer for SCell beam recovery timer (T_(S-BR))) for performingthe beam recovery operation for the SCell, and perform the beam recoveryoperation before the corresponding timer expires. Alternatively, theterminal may transmit a control message informing relevant informationto the PCell when the beam failure is declared after performing the beamrecovery operation for the SCell.

In the above-described procedure, the control message transmitted by theterminal to the SCell, the PUCCH SCell, or the PCell for notification ofthe beam failure detection or beam recovery failure of the SCell or forthe beam recovery may be transmitted through an uplink physical layerchannel, a MAC control element (CE), or an RRC control message.

When the terminal transmits the uplink physical layer channel to theSCell, the PUCCH SCell, or the PCell for notification of the beamfailure detection or beam recovery failure of the SCell or for the beamrecovery, the terminal may transmit a control field of the uplinkphysical layer channel using the uplink active BWP. Alternatively, anadditional physical layer signal configured for the beam recovery may betransmitted or a random access procedure may be performed.

For such the beam recovery operation, the base station (SCell, PUCCHSCell, or PCell) may transfer, to the terminal, configurationinformation such as parameters configuring the above-described RAresource, the physical layer signal for beam recovery, or the controlfield in the PUCCH through the connection reconfiguration (e.g., RRCconnection reconfiguration) message (the step S706 of FIG. 7) forsupporting CA functions. In this case, the parameters such as the RAresource for beam recovery, the physical layer signal for beam recovery,or the control field in the PUCCH may be configured on a SCell, SCellgroup, or beam basis for one or more BWPs configured in the terminal orthe active BWP. Here, being configured on a beam basis may mean that itis configured in association with a reference signal identifier (e.g.,an index of CSI-RS or SSB) for beam measurement (or beam monitoring) ora TCI state ID.

Accordingly, when the beam failure detection occurs in a certain SCell,the terminal may transmit, for the beam recovery, the above-described RAresource or the physical layer signal, which is configured on an SCell,SCell group, or beam basis, to the SCell, PUCCH SCell, or PCell, ortransmit the control field in the PUCCH to the PCell or PUCCH SCell, sothat the PCell or PUCCH SCell can identify the SCell and the servingbeam (or active beam) that is the target of beam recovery.

In the method in which the terminal transmit the MAC CE (or MAC controlPDU) or the RRC control message (e.g., beam recovery failure reportmessage, radio link failure (RLF) report message, radio linkre-establishment request message, or the like) to the SCell, PUCCHSCell, or PCell for notification of the beam failure detection or thebeam recovery failure, or for the beam recovery (BFR), the correspondingcontrol message may be transmitted as including at least one of thefollowing information or information obtained by conditionally combiningat least one of the following information.

Identifier (or index) of the cell where the beam failure detection orthe beam recovery procedure is performed or the cell where the RLFoccurs

-   -   Frequency information of the cell where the beam failure        detection or the beam recovery procedure is performed or the        cell where the RLF occurs    -   Identifier (or index) of the BWP where the beam failure        detection or the beam recovery procedure is performed or the BWP        where the RLF occurs    -   Identifier (or index) of the BWP where the beam failure        detection or the beam recovery procedure is performed or the BWP        where the RLF occurs, information for identifying a target beam        or candidate beam of the beam recovery (or, reconfiguration)        (e.g., TCI state ID, CSI-RS index, or SSB index)    -   Identifier (or index) of the BWP where the beam failure        detection or the beam recovery procedure is performed or the BWP        where the RLF occurs, beam measurement result information (e.g.,        SINR, SNR, RSRP, RSRQ, path loss measurement value, etc.)

Measurement result information (e.g., SINR, SNR, RSRP, RSRQ, path lossmeasurement value, etc.) of a candidate beam

-   -   Information on whether the condition for performing        non-contention-based random access is satisfied    -   Time point at which the beam failure detection or the radio link        failure is recognized    -   Information on a time elapsed after a time point at which the        beam recovery procedure is initiated or beam failure detection        (BFD) occurs, or information on the corresponding time point    -   Location information of the corresponding terminal at the time        of occurrence of beam failure detection (BFD), radio link        failure, or the like, or at the time at which the corresponding        control message is generated and transmitted (here, the location        information may be geolocation information, such as latitude or        longitude, or measurement result information from which the        location can be estimated)

For the ‘location information’ transmitted by the terminal, the basestation may transmit control information including at least one orconditionally combined information from the following information to theterminal using system information or a separate control message.

Timing information for location information measurement (or estimation)

-   -   Reference value for reporting measurement results    -   A range of measurement result values and an index corresponding        to each range of the measurement result values    -   Reference value for reporting geolocation information (e.g.        latitude/longitude, GPS information, or terminal built-in        positioning sensor information)    -   Fluctuation width (or fluctuation range) of the geolocation        information and index information corresponding thereto

Also, when transmitting the location information corresponding to anyone of the expressions as described above, the terminal may transmit thelocation information to the base station in form of at least one orconditionally combined information from the following information.

Information indicating whether the configured reference value issatisfied

-   -   Measurement result information    -   A range of measurement result values and an index corresponding        to each range of the measurement result values    -   Geolocation information    -   Fluctuation width (or fluctuation range) of the geolocation        information and index information corresponding thereto

In addition, the terminal may transmit control information forrequesting deactivation of the corresponding cell to the SCell, PUCCHSCell, or PCell. In addition, when the terminal transmits the beamfailure detection or beam recovery failure report, the beam recoveryrequest, the radio link failure (RLF) report, or the radio linkre-establishment request message through a MAC CE (or MAC control PDU)or an RRC control message, a logical channel identifier (LCID) fortransmitting the control message may be designated. That is, by usingonly the LCID of the MAC header (or subheader) of the MAC layer controlmessage, it may be identified that the corresponding MAC CE is controlinformation informing the beam failure detection or the beam recoveryfailure, or control information informing the beam recovery, the beamrecovery request, or the radio link failure report. In addition, whenthe MAC CE is configured to include the control parameter informationdescribed above, the corresponding control parameter or message may beconfigured to be distinguished using field information of the MACsubheader.

In case that the terminal transmits control information such as the beamfailure detection, the beam recovery failure report, or the radio linkfailure (RLF) report of the SCell through an uplink physical layercontrol channel (PUCCH) or a PUSCH using a PUCCH format, indicationinformation indicating that the corresponding situation has occurred,the identifier (or index) of the corresponding cell, the BWP identifierinformation, or the like may be transmitted. In this case, transmittingthrough the PUSCH using a PUCCH format may mean transmitting the controlinformation in a form that can be directly recognized by the physicallayer of the receiving side without involvement of the MAC layer (thatis, without MAC (sub)header). When the control information istransmitted through the PUCCH, the control information may betransmitted to the PUCCH SCell or the PCell, and a dedicated PUCCHresource may be allocated for this purpose. That is, the correspondingcontrol information may be transmitted using the PUCCH resourceallocated exclusively for the beam failure detection, the beam recoveryfailure report, or the radio link failure (RLF) report of the SCell. Ifthere is no pre-allocated resource or no available PUCCH resource, thecorresponding control information may be transmitted through a randomaccess procedure. When a non-contention-based random access procedure isperformed, the corresponding control information may be transmitted inform of a MAC CE or an RRC control message described above through anuplink resource scheduled first in the random access procedure. On theother hand, when a contention-based random access procedure isperformed, after completion of the random access procedure, thecorresponding control information may be transmitted in form of a MAC CEor an RRC control message described above after completion of the randomaccess procedure.

The PCell, that has been reported the beam failure detection or beamrecovery failure or received control information requesting deactivationof the corresponding cell through the SCell or PUCCH SCell or from theterminal, may deactivate the corresponding SCell and transmit to theSCell and/or the terminal a control message informing that the SCell hasbeen deactivated.

In addition, the SCell, PUCCH SCell, or PCell receiving the controlmessage of the above-described uplink physical layer channel (e.g.,PUCCH, PRACH, or PUSCH) from the terminal for beam recovery of the PCellor SCell may activate the corresponding SCell in case of successfullyfinishing the beam recovery procedure, and transmit, to the terminal,control information informing activation of the recovered beam by usinga downlink physical layer control channel (e.g., PDCCH) or a MAC CE ofthe SCell, PUCCH SCell, or PCell. In this case, the SCell, PUCCH SCell,or PCell may transmit control information informing activation of one ormore TCI state IDs to the terminal in form of a DCI or a UCI in thePDCCH or a MAC CE. In addition, if necessary, the SCell, PUCCH SCell, orPCell may transmit, to the terminal, an RRC control message forreconfiguring the configured TCI state information or reconfiguringconfiguration information of parameters for beam management or beamrecovery. In addition, when using cross-carrier scheduling to transmit aresponse message for the beam recovery from the terminal or to startdownlink channel transmission after the beam recovery, the base station(SCell, PUCCH SCell, or PCell) may transmit an identifier of thecorresponding cell and information for identifying the activated beam.The cell identifier or the beam identification information may be a TCIstate ID, a CSI-RS index, an SSB index, or the like, and may betransmitted to the terminal through a PDCCH or a PDSCH.

When the terminal detects a beam satisfying the beam recovery (orconfiguration) condition by monitoring (or measuring) beams of the SCellin the beam recovery procedure after the beam failure detection, theterminal may perform an RA operation to the SCell by using a randomaccess (RA) preamble resource corresponding to the beam. In this case,the random access procedure may use the contention-free random access orthe contention-based random access procedure.

When the terminal attempts the non-contention-based random accessprocedure for beam recovery after the beam failure detection of theSCell and fails the non-contention-based random access procedure, orwhen the reference condition for the non-contention-based random accessis not satisfied, the terminal may be controlled to perform acontention-based random access procedure to the SCell or PCell. That is,when a reference signal reception strength of the corresponding beam isgreater than or equal to a reference value, the non-contention-basedrandom access procedure may be performed, and when less than thereference value, the execution of the non-contention-based random accessprocedure may be restricted.

Here, the received signal strength of the reference signal used as thereference value for performing the non-contention-based random accessmay be represented by RSSI, SNR, RSRP, RSRQ, or the like of thecorresponding reference signal (e.g., CSI-RS or synchronization signaland PBCH block (SSB)).

In addition, a timer (e.g., Timer_X) that specifies a duration in whichthe non-contention-based random access procedure for beam recovery canbe performed may be configured, and the terminal may be configured toperform a contention-based random access procedure when thenon-contention-based random access procedure is not successfullycompleted until the corresponding timer expires.

Also, when the terminal performs the contention-based random accessprocedure for beam recovery, the terminal may transmit controlinformation including at least one of an identifier of the cell in whichthe beam failure detection or beam recovery procedure described above isperformed, information for identifying the corresponding beam,measurement result information of the corresponding beam, measurementresult information of the candidate beam, information on whether or notthe condition for performing the non-contention-based random access issatisfied, control information requesting deactivation of thecorresponding cell, information on a time elapsed from a time point atwhich the beam failure detection is recognized (or a time point ofstarting the beam recovery), or information of the corresponding timepoint. The candidate beam may refer to a beam which is not configuredthe corresponding terminal, but its measurement result satisfies thepreconfigured condition (e.g., a beam whose measurement result such asRSRP, RSRQ, SINR, etc. is equal to or greater than the referencecondition) as well as a beam configured and deactivated for thecorresponding terminal.

If the SCell is deactivated during the CA function support, theparameters configured for the radio link or beam management operationfor the corresponding SCell may be released, stopped, or reset. Inaddition, a timer (or a counter value of a timer) configured for theradio link or beam management operation may be stopped or suspended, orreset to an initial value, so that the operation (e.g., timer runningoperation) of the timer is controlled to be stopped.

If the SCell has been deactivated due to the beam failure detection,when the beam recovery for the SCell is completed according to the abovedescription, the SCell may be activated. If the beam recovery completionis not according to the RA procedure by the terminal to the SCell ortransmission of control information for beam recovery by the terminal,but according to a result of beam monitoring (or measuring) of theSCell, the terminal may report the completion of beam recovery for theSCell to the PCell or the SCell. The control message informing thecompletion of beam recovery for the SCell may be configured in form of aMAC CE, and may be transmitted through an uplink message (e.g., MSG3 inthe RA procedure) transmitted first after transmission of the RApreamble (PRACH) for random access.

The PCell that receives the control message indicating the completion ofbeam recovery for the SCell from the terminal may activate thecorresponding SCell, and transmit control information on the activationto the SCell and/or the terminal.

When the bandwidth part (BWP) scheme introduced in the NR system isapplied to the PCell or the SCell, the following method should beadditionally considered in performing the random access (RA) operationfor beam recovery.

The terminal may transmit a non-contention-based PRACH through an uplinkBWP in which a non-contention-based RA resource allocated in advance isconfigured. A response message (e.g., RA Response (RAR)) for the PRACHtransmitted for beam recovery may be received through a downlink (DL)BWP corresponding to an uplink (UL) BWP through the PRACH is transmitted(e.g., DL BWP whose identifier is identical to that of the correspondingUL BWP) or an initial DL BWP.

Upon receiving the PRACH for beam recovery from the terminal, the PCellor the SCell may transmit an identifier of an active BWP, an active TCIstate ID, information requesting a measurement report, or the like tothe terminal together with the received PRACH index through a randomaccess response (RAR) message or a PDCCH. In this case, the identifierof the active BWP may be downlink and/or uplink BWP identifiers. Also,the information requesting the measurement report may be composed of oneor more bits. When the information is composed of a single bit, thismeans an indicator requesting a measurement result for the configuredreference signal identifier, TCI state ID, and the like. When theinformation is composed of a plurality of bits, the corresponding bitinformation may indicate a reference signal identifier, a TCI state ID,or a preconfigured measurement target ID, which is a measurement target.

The terminal receiving the RAR message or the related PDCCH controlfield for the PRACH transmitted for beam recovery from the PCell or theSCell may receive necessary information by monitoring a downlink channelin the downlink BWP, and may perform an uplink transmission operation inthe uplink BWP according to the received active BWP ID. In addition,when the measurement result report is requested, the terminal maytransmit the measurement result for the measurement target to the PCellor SCell.

When the non-contention-based RA operation performed for beam recoveryfails or does not succeed or when the non-contention-based RA for beamrecovery is not configured, the terminal may perform a contention-basedRA operation procedure for beam recovery of the SCell.

When the contention-based RA operation procedure is performed for beamrecovery, the terminal may transmit a contention-based RACH through theactive uplink BWP or the configured uplink BWP of the correspondingSCell in which contention-based RA resources are configured. However,when the contention-based RA resources are not configured in the activeuplink BWP or uplink BWP configured for the SCell, the terminal maytransmit a contention-based PRACH through the configured active uplinkBWP, the uplink BWP, or the initial BWP. However, in case that theterminal performs the contention-based random access procedure, prioritymay be given to the contention-based RA resource of the PCell, or incase that the RA resource is not configured in the uplink active BWP,the terminal may be configured to perform the RA procedure by givingpriority to the contention-based RA resource of the cell configured asthe initial BWP.

The response message (e.g., RAR message) for the contention-based PRACHtransmitted for beam recovery may be received through a downlink BWPcorresponding to the uplink BWP through which the PRACH is transmitted(e.g., DL BWP having the same identifier for identifying the BWP).Alternatively, the terminal may receive the response message for thePRACH through the initial BWP of the SCell or the PCell.

Upon receiving the PRACH for beam recovery from the terminal, the PCellor the SCell may transmit the RA response message to the terminal. Uponreceiving the RA response message, the terminal may notify the beamfailure detection or beam recovery, or transmit a control fieldindicating a beam recovery request, an identifier of the SCell, or beammeasurement result together with its own identifier (e.g., C-RNTI).Here, the beam measurement result may include a received signal strength(e.g., information representing RSSI, RSRP, RSRQ, SIR, SNR, etc.) of thecorresponding reference signal measured, an identifier of the referencesignal, the TCI state ID, or the like. However, the measurement resultmay be composed of only the reference signal identifier or the TCI stateID without the received signal strength information. In this case, themeasurement result may include the reference signal identifiers or theTCI state IDs in the received signal strength order (or reverse order).

In the beam recovery procedure using the random access described above,the terminal may be configured to report only the measurement resultreceived above a preconfigured reference value. In addition, when arelated timer (e.g., TBR) expires during the random access procedure forbeam recovery, the radio link failure (RRF) due to the beam recoveryfailure described above may be determined and a radio linkre-establishment procedure may be performed. In this case, the terminalmay convert the random access procedure in progress for beam recoveryinto the radio link re-establishment request.

Therefore, during the non-contention-based RA operation, in the MSG3stage (first uplink transmission after PRACH transmission), the terminalmay transmit the radio link re-establishment message, in which the causeof the RLF is set to the beam recovery failure or the beam failure, tothe base station.

Also, in case of performing the contention-based RA operation, in theMSG5 (i.e., second uplink transmission after PRACH transmission) stage,the terminal may transmit the radio link re-establishment message, inwhich the cause of the RLF failure is set to the beam recovery failureor beam failure. However, even when performing the contention-based RAoperation, in the MSG3 stage, the terminal may be controlled to transmitthe radio link re-establishment message, in which the cause of the RLFfailure is set to the beam recovery failure or beam failure, togetherwith the identifier of the terminal.

In addition, in performing the non-contention-based RA for beam recoveryconfigured for the terminal, when the non-contention-based RA is notperformed because the RSRP (or RSRQ) reference value for thenon-contention-based PRACH transmission is not satisfied, the terminalmay be controlled to perform a beam recovery operation usingcontention-based RA resources if a preconfigured timer (e.g., Timer_Xdescribed above) expires. Here, not satisfying the RSRP (or RSRQ)reference value means that the signal quality of PRACH for the RAresource configured for beam recovery is lower than the reference valuefor the contention-free PRACH transmission. However, the signal qualityor reference value of the PRACH means the received signal strength ofthe reference signal (e.g., SSB, CSI-RS, etc.) that can be expressed bythe above-described RSSI, SNR, RSRP, or RSRQ.

If necessary, the base station may configure the terminal having notperformed the contention-based RA to perform a beam recovery operationby using a contention-based RA resource regardless of the Timer_Xoperation. In this case, the terminal may perform the beam recoveryoperation by transmitting a PRACH using a contention-based RA resourceaccording to its own decision or when a preconfigured condition issatisfied.

In addition, when performing the non-contention-based RA procedureconfigured to the terminal for beam recovery or other purposes, Timer_Xmay be started (or restarted) at the time when the terminal triggers thenon-contention-based RA procedure. Here, Timer_X means a timerconfigured for the terminal to wait without stopping or canceling thenon-contention-based RA procedure until the corresponding Timer_Xexpires when the reference value for performing the non-contention-basedPRACH transmission using the corresponding RA resource is not satisfied.That is, after Timer_X is started (or restarted), the terminal mayperforming measurement or monitoring on whether the reference signal formeasuring the PRACH quality of the non-contention-based RA resource isabove (or below) the reference value before the corresponding Timer_Xexpires. In addition, if the reference value condition of the PRACHquality is not satisfied, the terminal may not perform thenon-contention-based RA operation and may not switch to thecontention-based RA procedure until Timer_X expires. If thecorresponding Timer_X expires while not satisfying the reference valuefor the non-contention-based PRACH transmission, the terminal maytransmit the contention-based PRACH by switching to the contention-basedRA procedure or by changing to another BWP.

In addition to the above-described operation or procedure for beamfailure detection or beam recovery, a signaling (e.g., polling orprobing) procedure for estimating a beam state and determining whetherpacket transmission and reception are possible may be performed betweenthe terminal and the base station (serving cell (or node) such as SCell,PUCCH SCell, or PCell).

FIG. 8 is a sequence chart for explaining a radio link management methodin a carrier aggregation environment according to another exemplaryembodiment of the present invention.

In FIG. 8, for convenience of description, an operation of a single cellof the base station 802 and the terminal 801 is described. However, theoperation of the base station 802 and the terminal 801 to be describedlater may also be applied to a carrier aggregation environment where aplurality of cells (carriers) are aggregated.

The base station 802 may configure a first cell and configure aconnection between the first cell and the terminal 801 to provideservices (S803). In this case, when the carrier aggregation function isapplied, the terminal 801 may receive configuration information on oneor more secondary cells (e.g., the second cell) from the primary cell(e.g., the first cell) to perform the carrier aggregation function.

The terminal 801 may perform a monitoring operation on the beam using areference signal of a downlink channel of the first cell and perform areception operation on the downlink channel (S804). In addition, thebase station 802 may perform beam monitoring using a reference signal ofan uplink channel from the terminal 801 through the first cell, andperform a reception operation on the uplink channel (S804).

The terminal 801 may monitor the signal quality of the downlink channelthrough the operation of the step S804, and monitor whether downlinkfeedback information (e.g., HARQ ACK/NACK or other control signal) or aphysical layer control channel (PDCCH) for its uplink transmission isreceived from the first cell while satisfying a preconfigured condition.Also, the base station 802 may monitor the signal quality of the uplinkchannel from the terminal through the operation of the step S805, andmay monitor whether uplink feedback information (e.g., HARQ ACK/NACK) orother control signal) or a physical layer control channel (PUCCH) forthe downlink transmission through the first cell is received from theterminal while satisfying a preconfigured condition.

When a result of performing the step S804 or S805 does not meet thepreconfigured condition, the base station 802 or the terminal 801 mayindependently transmit a polling message. Here, the polling message maybe transmitted as configured in a control field (or bit) of a physicallayer control channel (e.g., PDCCH or PUCCH) or in form of a MAC CE.

For example, the base station 802 may determine to transmit a DL pollingmessage through the step S805. In the step S805, the base station 802may start a timer (e.g., DL_POLL_TIMER) for a polling operation, andgenerate and transmit a DL polling message through the first cell(S806). The terminal 801 receiving the DL polling message of the stepS806 may transmit a DL polling response message or generate and transmita UL polling message (S807).

Before the DL_POLL_TIMER started in the step S805 expires, if the basestation 802 receives the DL polling response message or the UL pollingmessage from the terminal 801 through the first cell, the base station802 may determine that the corresponding beam (or radio link) is valid,and continue services using the corresponding beam (or radio link). Onthe other hand, if the DL polling response message or the UL pollingmessage is not received from the terminal 801 through the first cell andthe DL_POLL_TIMER expires, the base station 802 may declare a beam (orradio link) failure between the first cell and the terminal, and triggera beam recovery procedure or stop the downlink transmission for apreconfigured time interval (or timer). In addition, when the CAfunction is configured, the base station may deactivate the first cell.

In addition, in response to the DL polling message in the step S806, theterminal 801 may transmit a DL polling response message, or generate aUL polling message and transmit the UL polling message to the basestation 802 through the first cell (S807). That is, even when there isnot the step S806, the terminal may trigger the UL polling messagetransmission based on the result of the step S804. The terminal 801 thattriggers the UL polling message transmission may start UL_POLL_TIMER andgenerate and transmit the UL polling message.

The base station 802 receiving the UL polling message from the terminal801 through the first cell may transmit a UL polling response message(S808). If the base station 802 receives the UL polling message of thestep S807 without the step S806, the base station 802 may generate andtransmit a DL polling message in response to the UL polling instead ofthe UL polling response message.

When the UL polling response message or the UL polling message isreceived from the base station 802 through the first cell before theUL_POLL_TIMER started in the step S807 expires, the terminal 801 maydetermines that a beam (or radio link) between the first cell and theterminal is valid, and continue services by using the corresponding beam(or radio link).

However, when the UL polling response message or the DL polling messagefrom the base station 802 is not received through the first cell andUL_POLL_TIMER expires, the terminal 801 may declare a beam (or radiolink) failure between the terminal and the first cell, and trigger abeam recovery procedure or stop uplink transmission for a preconfiguredtime interval (or timer) (S809). In addition, when the CA function isconfigured, the terminal 801 may report the beam failure for the firstcell or request deactivation of the first cell through another servingcell (e.g., the second cell).

The polling response message described above may be transmitted asconfigured in a control field (or bit) of a physical layer controlchannel (e.g., PDCCH or PUCCH) or in form of a MAC CE.

The configuration parameter information on the timer value, thereference value, or the conditions required in the operation orprocedure for beam failure detection or beam recovery described abovemay be transmitted by the base station to the terminal through systeminformation or a separate control message.

In addition, in the above description, the operation of the base station(or cell) may be an operation performed by a node such as CU or DUdescribed with reference to FIG. 4 when the functional split function isapplied.

With respect to the operation of the timer defined or described in thepresent invention, although operations such as start, stop, reset,restart, or expire of the defined timer are not separately described,they mean or include the operations of the corresponding timer or acounter for the corresponding timer.

The cell (or base station) of the present invention may refer to a roadside unit (RSU), a radio remote head (RRH), a transmission point (TP), atransmission and reception point (TRP), or a gNB, in addition to theNodeB, the evolved NodeB, the base transceiver station (BTS), the radiobase station, the radio transceiver, the access point, or the accessnode as the base station described in FIG. 1. It may also be referred toas a CU node or a DU node according to application of the functionalsplit described in FIG. 4.

Also, the terminal of the present invention may refer to an Internet ofThing (IoT) device, a mounted module/device/terminal, or an on boarddevice/terminal, in addition to the terminal, the access terminal, themobile terminal, the station, the subscriber station, the mobilestation, the mobile subscriber station, the node, or the device as theUE described in FIG. 1.

The exemplary embodiments of the present disclosure may be implementedas program instructions executable by a variety of computers andrecorded on a computer readable medium. The computer readable medium mayinclude a program instruction, a data file, a data structure, or acombination thereof. The program instructions recorded on the computerreadable medium may be designed and configured specifically for thepresent disclosure or can be publicly known and available to those whoare skilled in the field of computer software.

Examples of the computer readable medium may include a hardware devicesuch as ROM, RAM, and flash memory, which are specifically configured tostore and execute the program instructions. Examples of the programinstructions include machine codes made by, for example, a compiler, aswell as high-level language codes executable by a computer, using aninterpreter. The above exemplary hardware device can be configured tooperate as at least one software module in order to perform theembodiments of the present disclosure, and vice versa.

While the embodiments of the present disclosure and their advantageshave been described in detail, it should be understood that variouschanges, substitutions and alterations may be made herein withoutdeparting from the scope of the present disclosure.

1.-20. (canceled)
 21. An operation method of a terminal for beammanagement and radio link management, the operation method comprising:receiving, from a first cell operating as a primary cell (PCell), aconnection reconfiguration message for configuring a carrier aggregationfunction including configuration information for a second cell operatingas a secondary cell (SCell); performing beam monitoring operations forthe first cell and the second cell and a radio link monitoring operationfor the first cell; in response to detecting a beam failure for thesecond cell, performing a procedure of a beam failure recovery for thesecond cell, and reporting the beam failure recovery to the first cellor the second cell; and in response to detecting a radio link failure(RLF) for the first cell, re-establishing a radio link with a thirdcell, and performing a procedure of reporting the RLF to the third cell.22. The operation method of claim 21, wherein the procedure of reportingthe RLF to the third cell includes transmitting a RLF message to thethird cell, the RLF message including at least one of an identifier ofthe first cell where the RLF occurred, location information of theterminal at a time of the occurrence of the RLF, and information on atime elapsed after the occurrence of the RLF.
 23. The operation methodof claim 22, wherein the RLF message is a radio resource control (RRC)layer message.
 24. The operation method of claim 22, wherein the RLFmessage further includes information on whether a condition forperforming a random access procedure for beam recovery is satisfied, andthe random access procedure is a non-contention-based random accessprocedure.
 25. The operation method of claim 22, wherein the locationinformation includes a latitude and/or a longitude of the terminal. 26.The operation method of claim 21, wherein the procedure of reporting thebeam failure recovery to the first cell includes transmitting a mediumaccess control (MAC) message including at least one of information foridentifying a failed beam, information on a time elapsed from thedetection of the beam failure, and information on a time elapsed fromthe detection of the beam failure to completion of the beam failurerecovery.
 27. The operation method of claim 26, wherein the informationof identifying the failed beam is a transmission configuration indicator(TCI) state identifier or an identifier of a reference signal for beammonitoring.
 28. The operation method of claim 26, wherein the MACmessage is a MAC control element (CE) message.
 29. An operation methodof a base station operating a first cell and a second cell, the firstcell being a primary cell (PCell), and the operation method comprising:transmitting, to a terminal, a connection reconfiguration message forconfiguring a carrier aggregation function including configurationinformation on the second cell operating as a secondary cell (SCell); inresponse to detecting a beam failure for the second cell at theterminal, performing a procedure of receiving a report of a beam failurerecovery from the terminal via the first cell or the second cell, thebeam failure recovery being performed by the terminal for the secondcell; and in response to detecting a radio link failure (RLF) for thefirst cell at the terminal, performing a procedure of receiving a reportof the RLF from the terminal via a third cell.
 30. The operation methodof claim 29, wherein the procedure of receiving the report of the RLFincludes receiving a RLF message from the terminal via the third cell,the RLF message including at least one of an identifier of the firstcell where the RLF occurred, location information of the terminal at atime of the occurrence of the RLF, and information on a time elapsedafter the occurrence of the RLF.
 31. The operation method of claim 30,wherein the RLF message is a radio resource control (RRC) layer message.32. The operation method of claim 30, wherein the RLF message furtherincludes information on whether a condition for performing a randomaccess procedure for beam recovery is satisfied, and the random accessprocedure is a non-contention-based random access procedure.
 33. Theoperation method of claim 30, wherein the location information includesa latitude and/or a longitude of the terminal.
 34. The operation methodof claim 30, wherein the procedure of receiving the report of the beamfailure recovery includes receiving a medium access control (MAC)message including at least one of information for identifying a failedbeam, information on a time elapsed from the detection of the beamfailure, and information on a time elapsed from the detection of thebeam failure to completion of the beam failure recovery.
 35. Theoperation method of claim 34, wherein the information of identifying thefailed beam is a transmission configuration indicator (TCI) stateidentifier or an identifier of a reference signal for beam monitoring.36. The operation method of claim 34, wherein the MAC message is a MACcontrol element (CE) message.